1. Field of the Invention
The present invention relates to a mold clamping mechanism for an injection molding machine.
2. Description of the Related Art
An injection molding machine includes an injection apparatus and a mold clamping mechanism on a machine base. The mold clamping mechanism includes a fixed platen installed on the machine base, a plurality of tie bars fixed to an edge portion of the fixed platen, a movable platen that is movably installed along the tie bars, and a toggle mechanism that drives the movable platen. A fixed-side mold is attached to the fixed platen at a surface facing the movable platen. Further, a movable-side mold is attached to the movable platen at a surface facing the fixed platen. The mold is closed/opened by moving the movable platen toward the fixed platen (moving forward) and moving the movable platen in a direction away from the fixed platen (moving backward). A resin that is heated and melted in a heating cylinder of the injection apparatus is injected from an injection nozzle, fills a cavity space in the mold, and is cooled and solidified in the cavity space, whereby a molded article is obtained.
Japanese Patent Application Laid-Open No. 2010-36348 describes a mold clamping mechanism for an injection molding machine, in which a mold platen (a fixed platen, a movable platen) is configured by a molding die and a mold attachment die that is placed so as to be attachable to and detachable from the molding die, wherein a mold (a fixed-side mold, a movable-side mold) is attached to the mold attachment die. A mold-attachment receiving element is formed on the mold attachment surface of the mold attachment die so as to fit attachment elements of a plurality of molds having different specifications.
Japanese Patent Application Laid-Open No. 2005-205819 describes a mold clamping apparatus for an injection molding machine, in which a fixed platen is configured by a main body that supports end parts of tie bars and a mold fixing member fixed to the main body, wherein a fixed-side mold is attached to the mold fixing member. The structure of the mold clamping apparatus can achieve an increase in stiffness of the fixed platen, can suppress contact surfaces of the fixed-side mold and a movable-side mold from separating from each other at the time of mold clamping, and can achieve a reduction in weight of the fixed platen.
Further, Japanese Patent Application Laid-Open No. 09-155929 describes an injection molding machine, in which the entire mold attachment surface of each of a fixed platen and a movable platen is covered by a liner having a smooth surface, a high hardness, and a high corrosion resistance, wherein the liner is secured to each of the fixed platen and the movable platen by means of a securing tool that is configured so as not to protrude on the surface.
As described above, a mold clamping mechanism for an injection molding machine includes two mold platens, that is, a fixed platen fixed to a machine base and a movable platen that is placed so as to be movable and parallel to the fixed platen. A fixed-side mold is attached to the fixed platen, a movable-side mold is attached to the movable platen, and the mold is closed/opened and clamped by moving the movable platen forward/backward with respect to the fixed platen.
If the stiffness of the mold platen (the fixed platen, the movable platen) is low, the mold (the fixed-side mold, the movable-side mold) deforms together with the mold platen under the application of mold clamping power or injection pressure, so that the precision of a molded article may decrease in some cases. The required stiffness of a mold platen is determined depending on the used mold. In general, mold platens need to have a stiffness high enough to support even a mold that requires stiffness, and hence mold platens are provided with an excessive stiffness in some cases. If a mold platen is made thicker in order to enhance the stiffness of the mold platen, the total machine length is larger, costs are higher, and a space to be secured for machine installation is larger.
According to the technique described in Japanese Patent Application Laid-Open No. 2010-36348 mentioned above, the mold attachment die is added to the molding die in order to increase the degree of freedom in mold selection, and it is not assumed that the mold is attached to the molding die in the state where the mold attachment die is detached from the molding die. Further, this technique does not have an object to adjust the stiffness of the mold platen.
Further, the technique described in Japanese Patent Application Laid-Open No. 09-155929 mentioned above is intended to protect the mold surface, and does not have an object to adjust the stiffness of the mold platen.